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It is to be observed, then, that the wings in all hemimetabolous insects are outgrowths from the notum, and not from the flanks or pleurum of the thorax. There is, then, no structure in any other part of the body with which they are homologous.

Fig. 157.—Development of wings of Trichoptera: A, portion of body-wall of young larva of Trichostegia; ch, cuticula, forming at r a projection into the hypodermis, m; r, and d, forming thus the first rudiment of the wing. B, the parts in a larva of nearly full size; a, c, d, b, the well-developed hypodermis of the wing-germ separated into two parts by r, the penetrating extension of the cuticula; v, mesoderm, C, wing-pad of another Phryganeid freed from its case at its change to the pupa: b, d, outer layer of the hypodermis (m) of the body-wall; v, inner layer within nuclei.—After Dewitz, from Sharp.

The same may be said of the true Neuroptera, Trichoptera (Fig. 157), the Coleoptera, and the Diptera, Lepidoptera, and Hymenoptera. As we have observed in the house fly,^[27] the wings are evidently outgrowths of the meso- and metanotum; we have also observed this to be most probably the case in the Lepidoptera, from observations on a Tortrix in different stages of metamorphosis. It is also the case with the Hymenoptera, as we have observed in bees and wasps;^[28] and in these forms, and probably all Hymenoptera, the wings are outgrowths of the scutal region of the notum.